The Vestimentifera and the Pogonophora have complex taxonomic histories, reviewed in Rouse (2001a). However, the roughly 150 species are clearly members of the phylum Annelida and jointly form the family Siboglinidae (Rouse 2001a, b). The consequence of this devaluation in standing is that a complex superstructure of classes, orders, and families has lost its taxonomic value entirely.